Hi, 93 240 Wagon, I cut the coolant line on the drivers side of the heater control valve and installed a generic in line ball valve along with the Volvo valve that is malfunctioning. With the generic ball valve in the closed position the vents are still pumping out only hot air. I was speaking with an aquaintance of mine the other day who happens to be a BMW tech. He says that hot coolant always gets to the heater core no matter what position the valve is in, and that it's a mechanical flap in the vent system that blocks off the hot air from the vents. He claims that just installing a ball valve will not get the job done. Of course I think he's slightly confused, with the valve closed, how can hot coolant get to the heater core? I have to admit though, I am also confused as to why it's still blowing out hot air. The valve worked fine in the truck I borrowed it from. Any help would be appreciated.